1 /*
   2  * Copyright (c) 1997, 2016, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_ASM_ASSEMBLER_HPP
  26 #define SHARE_VM_ASM_ASSEMBLER_HPP
  27 
  28 #include "asm/codeBuffer.hpp"
  29 #include "asm/register.hpp"
  30 #include "code/oopRecorder.hpp"
  31 #include "code/relocInfo.hpp"
  32 #include "memory/allocation.hpp"
  33 #include "runtime/vm_version.hpp"
  34 #include "utilities/debug.hpp"
  35 #include "utilities/growableArray.hpp"
  36 #include "utilities/macros.hpp"
  37 
  38 // This file contains platform-independent assembler declarations.
  39 
  40 class MacroAssembler;
  41 class AbstractAssembler;
  42 class Label;
  43 
  44 /**
  45  * Labels represent destinations for control transfer instructions.  Such
  46  * instructions can accept a Label as their target argument.  A Label is
  47  * bound to the current location in the code stream by calling the
  48  * MacroAssembler's 'bind' method, which in turn calls the Label's 'bind'
  49  * method.  A Label may be referenced by an instruction before it's bound
  50  * (i.e., 'forward referenced').  'bind' stores the current code offset
  51  * in the Label object.
  52  *
  53  * If an instruction references a bound Label, the offset field(s) within
  54  * the instruction are immediately filled in based on the Label's code
  55  * offset.  If an instruction references an unbound label, that
  56  * instruction is put on a list of instructions that must be patched
  57  * (i.e., 'resolved') when the Label is bound.
  58  *
  59  * 'bind' will call the platform-specific 'patch_instruction' method to
  60  * fill in the offset field(s) for each unresolved instruction (if there
  61  * are any).  'patch_instruction' lives in one of the
  62  * cpu/<arch>/vm/assembler_<arch>* files.
  63  *
  64  * Instead of using a linked list of unresolved instructions, a Label has
  65  * an array of unresolved instruction code offsets.  _patch_index
  66  * contains the total number of forward references.  If the Label's array
  67  * overflows (i.e., _patch_index grows larger than the array size), a
  68  * GrowableArray is allocated to hold the remaining offsets.  (The cache
  69  * size is 4 for now, which handles over 99.5% of the cases)
  70  *
  71  * Labels may only be used within a single CodeSection.  If you need
  72  * to create references between code sections, use explicit relocations.
  73  */
  74 class Label VALUE_OBJ_CLASS_SPEC {
  75  private:
  76   enum { PatchCacheSize = 4 };
  77 
  78   // _loc encodes both the binding state (via its sign)
  79   // and the binding locator (via its value) of a label.
  80   //
  81   // _loc >= 0   bound label, loc() encodes the target (jump) position
  82   // _loc == -1  unbound label
  83   int _loc;
  84 
  85   // References to instructions that jump to this unresolved label.
  86   // These instructions need to be patched when the label is bound
  87   // using the platform-specific patchInstruction() method.
  88   //
  89   // To avoid having to allocate from the C-heap each time, we provide
  90   // a local cache and use the overflow only if we exceed the local cache
  91   int _patches[PatchCacheSize];
  92   int _patch_index;
  93   GrowableArray<int>* _patch_overflow;
  94 
  95   Label(const Label&) { ShouldNotReachHere(); }
  96  protected:
  97 
  98   // The label will be bound to a location near its users.
  99   bool _is_near;
 100 
 101  public:
 102 
 103   /**
 104    * After binding, be sure 'patch_instructions' is called later to link
 105    */
 106   void bind_loc(int loc) {
 107     assert(loc >= 0, "illegal locator");
 108     assert(_loc == -1, "already bound");
 109     _loc = loc;
 110   }
 111   void bind_loc(int pos, int sect) { bind_loc(CodeBuffer::locator(pos, sect)); }
 112 
 113 #ifndef PRODUCT
 114   // Iterates over all unresolved instructions for printing
 115   void print_instructions(MacroAssembler* masm) const;
 116 #endif // PRODUCT
 117 
 118   /**
 119    * Returns the position of the the Label in the code buffer
 120    * The position is a 'locator', which encodes both offset and section.
 121    */
 122   int loc() const {
 123     assert(_loc >= 0, "unbound label");
 124     return _loc;
 125   }
 126   int loc_pos()  const { return CodeBuffer::locator_pos(loc()); }
 127   int loc_sect() const { return CodeBuffer::locator_sect(loc()); }
 128 
 129   bool is_bound() const    { return _loc >=  0; }
 130   bool is_unbound() const  { return _loc == -1 && _patch_index > 0; }
 131   bool is_unused() const   { return _loc == -1 && _patch_index == 0; }
 132 
 133   // The label will be bound to a location near its users. Users can
 134   // optimize on this information, e.g. generate short branches.
 135   bool is_near()           { return _is_near; }
 136 
 137   /**
 138    * Adds a reference to an unresolved displacement instruction to
 139    * this unbound label
 140    *
 141    * @param cb         the code buffer being patched
 142    * @param branch_loc the locator of the branch instruction in the code buffer
 143    */
 144   void add_patch_at(CodeBuffer* cb, int branch_loc);
 145 
 146   /**
 147    * Iterate over the list of patches, resolving the instructions
 148    * Call patch_instruction on each 'branch_loc' value
 149    */
 150   void patch_instructions(MacroAssembler* masm);
 151 
 152   void init() {
 153     _loc = -1;
 154     _patch_index = 0;
 155     _patch_overflow = NULL;
 156     _is_near = false;
 157   }
 158 
 159   Label() {
 160     init();
 161   }
 162 };
 163 
 164 // A NearLabel must be bound to a location near its users. Users can
 165 // optimize on this information, e.g. generate short branches.
 166 class NearLabel : public Label {
 167  public:
 168   NearLabel() : Label() { _is_near = true; }
 169 };
 170 
 171 // A union type for code which has to assemble both constant and
 172 // non-constant operands, when the distinction cannot be made
 173 // statically.
 174 class RegisterOrConstant VALUE_OBJ_CLASS_SPEC {
 175  private:
 176   Register _r;
 177   intptr_t _c;
 178 
 179  public:
 180   RegisterOrConstant(): _r(noreg), _c(0) {}
 181   RegisterOrConstant(Register r): _r(r), _c(0) {}
 182   RegisterOrConstant(intptr_t c): _r(noreg), _c(c) {}
 183 
 184   Register as_register() const { assert(is_register(),""); return _r; }
 185   intptr_t as_constant() const { assert(is_constant(),""); return _c; }
 186 
 187   Register register_or_noreg() const { return _r; }
 188   intptr_t constant_or_zero() const  { return _c; }
 189 
 190   bool is_register() const { return _r != noreg; }
 191   bool is_constant() const { return _r == noreg; }
 192 };
 193 
 194 // The Abstract Assembler: Pure assembler doing NO optimizations on the
 195 // instruction level; i.e., what you write is what you get.
 196 // The Assembler is generating code into a CodeBuffer.
 197 class AbstractAssembler : public ResourceObj  {
 198   friend class Label;
 199 
 200  protected:
 201   CodeSection* _code_section;          // section within the code buffer
 202   OopRecorder* _oop_recorder;          // support for relocInfo::oop_type
 203 
 204  public:
 205   // Code emission & accessing
 206   address addr_at(int pos) const { return code_section()->start() + pos; }
 207 
 208  protected:
 209   // This routine is called with a label is used for an address.
 210   // Labels and displacements truck in offsets, but target must return a PC.
 211   address target(Label& L)             { return code_section()->target(L, pc()); }
 212 
 213   bool is8bit(int x) const             { return -0x80 <= x && x < 0x80; }
 214   bool isByte(int x) const             { return 0 <= x && x < 0x100; }
 215   bool isShiftCount(int x) const       { return 0 <= x && x < 32; }
 216 
 217   // Instruction boundaries (required when emitting relocatable values).
 218   class InstructionMark: public StackObj {
 219    private:
 220     AbstractAssembler* _assm;
 221 
 222    public:
 223     InstructionMark(AbstractAssembler* assm) : _assm(assm) {
 224       assert(assm->inst_mark() == NULL, "overlapping instructions");
 225       _assm->set_inst_mark();
 226     }
 227     ~InstructionMark() {
 228       _assm->clear_inst_mark();
 229     }
 230   };
 231   friend class InstructionMark;
 232 #ifdef ASSERT
 233   // Make it return true on platforms which need to verify
 234   // instruction boundaries for some operations.
 235   static bool pd_check_instruction_mark();
 236 
 237   // Add delta to short branch distance to verify that it still fit into imm8.
 238   int _short_branch_delta;
 239 
 240   int  short_branch_delta() const { return _short_branch_delta; }
 241   void set_short_branch_delta()   { _short_branch_delta = 32; }
 242   void clear_short_branch_delta() { _short_branch_delta = 0; }
 243 
 244   class ShortBranchVerifier: public StackObj {
 245    private:
 246     AbstractAssembler* _assm;
 247 
 248    public:
 249     ShortBranchVerifier(AbstractAssembler* assm) : _assm(assm) {
 250       assert(assm->short_branch_delta() == 0, "overlapping instructions");
 251       _assm->set_short_branch_delta();
 252     }
 253     ~ShortBranchVerifier() {
 254       _assm->clear_short_branch_delta();
 255     }
 256   };
 257 #else
 258   // Dummy in product.
 259   class ShortBranchVerifier: public StackObj {
 260    public:
 261     ShortBranchVerifier(AbstractAssembler* assm) {}
 262   };
 263 #endif
 264 
 265  public:
 266 
 267   // Creation
 268   AbstractAssembler(CodeBuffer* code);
 269 
 270   // ensure buf contains all code (call this before using/copying the code)
 271   void flush();
 272 
 273   void emit_int8(   int8_t  x) { code_section()->emit_int8(   x); }
 274   void emit_int16(  int16_t x) { code_section()->emit_int16(  x); }
 275   void emit_int32(  int32_t x) { code_section()->emit_int32(  x); }
 276   void emit_int64(  int64_t x) { code_section()->emit_int64(  x); }
 277 
 278   void emit_float(  jfloat  x) { code_section()->emit_float(  x); }
 279   void emit_double( jdouble x) { code_section()->emit_double( x); }
 280   void emit_address(address x) { code_section()->emit_address(x); }
 281 
 282   // min and max values for signed immediate ranges
 283   static int min_simm(int nbits) { return -(intptr_t(1) << (nbits - 1))    ; }
 284   static int max_simm(int nbits) { return  (intptr_t(1) << (nbits - 1)) - 1; }
 285 
 286   // Define some:
 287   static int min_simm10() { return min_simm(10); }
 288   static int min_simm13() { return min_simm(13); }
 289   static int min_simm16() { return min_simm(16); }
 290 
 291   // Test if x is within signed immediate range for nbits
 292   static bool is_simm(intptr_t x, int nbits) { return min_simm(nbits) <= x && x <= max_simm(nbits); }
 293 
 294   // Define some:
 295   static bool is_simm5( intptr_t x) { return is_simm(x, 5 ); }
 296   static bool is_simm8( intptr_t x) { return is_simm(x, 8 ); }
 297   static bool is_simm10(intptr_t x) { return is_simm(x, 10); }
 298   static bool is_simm11(intptr_t x) { return is_simm(x, 11); }
 299   static bool is_simm12(intptr_t x) { return is_simm(x, 12); }
 300   static bool is_simm13(intptr_t x) { return is_simm(x, 13); }
 301   static bool is_simm16(intptr_t x) { return is_simm(x, 16); }
 302   static bool is_simm26(intptr_t x) { return is_simm(x, 26); }
 303   static bool is_simm32(intptr_t x) { return is_simm(x, 32); }
 304 
 305   // Accessors
 306   CodeSection*  code_section() const   { return _code_section; }
 307   CodeBuffer*   code()         const   { return code_section()->outer(); }
 308   int           sect()         const   { return code_section()->index(); }
 309   address       pc()           const   { return code_section()->end();   }
 310   int           offset()       const   { return code_section()->size();  }
 311   int           locator()      const   { return CodeBuffer::locator(offset(), sect()); }
 312 
 313   OopRecorder*  oop_recorder() const   { return _oop_recorder; }
 314   void      set_oop_recorder(OopRecorder* r) { _oop_recorder = r; }
 315 
 316   address       inst_mark() const { return code_section()->mark();       }
 317   void      set_inst_mark()       {        code_section()->set_mark();   }
 318   void    clear_inst_mark()       {        code_section()->clear_mark(); }
 319 
 320   // Constants in code
 321   void relocate(RelocationHolder const& rspec, int format = 0) {
 322     assert(!pd_check_instruction_mark()
 323         || inst_mark() == NULL || inst_mark() == code_section()->end(),
 324         "call relocate() between instructions");
 325     code_section()->relocate(code_section()->end(), rspec, format);
 326   }
 327   void relocate(   relocInfo::relocType rtype, int format = 0) {
 328     code_section()->relocate(code_section()->end(), rtype, format);
 329   }
 330 
 331   static int code_fill_byte();         // used to pad out odd-sized code buffers
 332 
 333   // Associate a comment with the current offset.  It will be printed
 334   // along with the disassembly when printing nmethods.  Currently
 335   // only supported in the instruction section of the code buffer.
 336   void block_comment(const char* comment);
 337   // Copy str to a buffer that has the same lifetime as the CodeBuffer
 338   const char* code_string(const char* str);
 339 
 340   // Label functions
 341   void bind(Label& L); // binds an unbound label L to the current code position
 342 
 343   // Move to a different section in the same code buffer.
 344   void set_code_section(CodeSection* cs);
 345 
 346   // Inform assembler when generating stub code and relocation info
 347   address    start_a_stub(int required_space);
 348   void       end_a_stub();
 349   // Ditto for constants.
 350   address    start_a_const(int required_space, int required_align = sizeof(double));
 351   void       end_a_const(CodeSection* cs);  // Pass the codesection to continue in (insts or stubs?).
 352 
 353   // constants support
 354   //
 355   // We must remember the code section (insts or stubs) in c1
 356   // so we can reset to the proper section in end_a_const().
 357   address int_constant(jint c) {
 358     CodeSection* c1 = _code_section;
 359     address ptr = start_a_const(sizeof(c), sizeof(c));
 360     if (ptr != NULL) {
 361       emit_int32(c);
 362       end_a_const(c1);
 363     }
 364     return ptr;
 365   }
 366   address long_constant(jlong c) {
 367     CodeSection* c1 = _code_section;
 368     address ptr = start_a_const(sizeof(c), sizeof(c));
 369     if (ptr != NULL) {
 370       emit_int64(c);
 371       end_a_const(c1);
 372     }
 373     return ptr;
 374   }
 375   address double_constant(jdouble c) {
 376     CodeSection* c1 = _code_section;
 377     address ptr = start_a_const(sizeof(c), sizeof(c));
 378     if (ptr != NULL) {
 379       emit_double(c);
 380       end_a_const(c1);
 381     }
 382     return ptr;
 383   }
 384   address float_constant(jfloat c) {
 385     CodeSection* c1 = _code_section;
 386     address ptr = start_a_const(sizeof(c), sizeof(c));
 387     if (ptr != NULL) {
 388       emit_float(c);
 389       end_a_const(c1);
 390     }
 391     return ptr;
 392   }
 393   address address_constant(address c) {
 394     CodeSection* c1 = _code_section;
 395     address ptr = start_a_const(sizeof(c), sizeof(c));
 396     if (ptr != NULL) {
 397       emit_address(c);
 398       end_a_const(c1);
 399     }
 400     return ptr;
 401   }
 402   address address_constant(address c, RelocationHolder const& rspec) {
 403     CodeSection* c1 = _code_section;
 404     address ptr = start_a_const(sizeof(c), sizeof(c));
 405     if (ptr != NULL) {
 406       relocate(rspec);
 407       emit_address(c);
 408       end_a_const(c1);
 409     }
 410     return ptr;
 411   }
 412 
 413   // Bootstrapping aid to cope with delayed determination of constants.
 414   // Returns a static address which will eventually contain the constant.
 415   // The value zero (NULL) stands instead of a constant which is still uncomputed.
 416   // Thus, the eventual value of the constant must not be zero.
 417   // This is fine, since this is designed for embedding object field
 418   // offsets in code which must be generated before the object class is loaded.
 419   // Field offsets are never zero, since an object's header (mark word)
 420   // is located at offset zero.
 421   RegisterOrConstant delayed_value(int(*value_fn)(), Register tmp, int offset = 0);
 422   RegisterOrConstant delayed_value(address(*value_fn)(), Register tmp, int offset = 0);
 423   virtual RegisterOrConstant delayed_value_impl(intptr_t* delayed_value_addr, Register tmp, int offset) = 0;
 424   // Last overloading is platform-dependent; look in assembler_<arch>.cpp.
 425   static intptr_t* delayed_value_addr(int(*constant_fn)());
 426   static intptr_t* delayed_value_addr(address(*constant_fn)());
 427   static void update_delayed_values();
 428 
 429   // Bang stack to trigger StackOverflowError at a safe location
 430   // implementation delegates to machine-specific bang_stack_with_offset
 431   void generate_stack_overflow_check( int frame_size_in_bytes );
 432   virtual void bang_stack_with_offset(int offset) = 0;
 433 
 434 
 435   /**
 436    * A platform-dependent method to patch a jump instruction that refers
 437    * to this label.
 438    *
 439    * @param branch the location of the instruction to patch
 440    * @param masm the assembler which generated the branch
 441    */
 442   void pd_patch_instruction(address branch, address target);
 443 
 444 };
 445 
 446 #include CPU_HEADER(assembler)
 447 
 448 #endif // SHARE_VM_ASM_ASSEMBLER_HPP
--- EOF ---